Multi-resolution fingerprint sensor

Abstract

Multi-resolution fingerprint sensors and methods of using the same are provided. The multi-resolution fingerprint sensors each include a portion of the imaging area or region of the sensor that provides higher imaging resolution than the remaining imaging area of the sensor. The area of higher resolution is useful for anti-spoofing purposes, but because only a portion of the sensor is higher-resolution, advantageously it will not impact hardware costs nearly as much as a sensor that was higher resolution over its entire imaging area. Furthermore, the higher resolution area can be down-sampled so there would be no impact on the standard matcher and image processing software stack, which expects a uniform resolution for the entire image acquired.

The invention claimed is: 
     
       1. A method of processing an image obtained with a multi-resolution biometric sensor having a first sensing region and second sensing region, the first sensing region having a resolution lower than a resolution of the second sensing region, the method comprising:
 acquiring a first image of an input object, the first image including an area of the input object imaged by only the second sensing region of the multi-resolution biometric sensor; 
 acquiring a second image of the input object, the second image including an area of the input object imaged by the first sensing region and an area of the input object imaged simultaneously by the second sensing region of the multi-resolution biometric sensor; and 
 processing each of the first image and the second image to determine biometric information of the input object. 
 
     
     
       2. The method of  claim 1 , wherein the first sensing region at least partially circumscribes the second sensing region. 
     
     
       3. The method of  claim 1 , wherein the first image and the second image are imaged separately in time, wherein the second image is acquired with the second sensing region operating in a low resolution mode such that the second image has a uniform resolution at the resolution corresponding to the first sensing region. 
     
     
       4. The method of  claim 3 , wherein the second region operating in the low resolution mode includes addressing a portion of address lines of the second sensing region. 
     
     
       5. The method of  claim 1 , wherein an initial image of the input object is imaged using both the first sensing region and the second sensing region simultaneously,
 wherein the acquiring the first image includes cropping the initial image to remove the area of the input object imaged by the first sensing region, and 
 wherein the acquiring the second image includes adjusting a resolution of the area of the input object imaged by the second sensing region to match the resolution of the first sensing region to produce a uniform-resolution image. 
 
     
     
       6. The method of  claim 5 , wherein the adjusting the resolution includes down-sampling the area of the input object imaged by the second sensing region. 
     
     
       7. The method of  claim 1 , wherein the input object includes a fingerprint. 
     
     
       8. The method of  claim 7 , wherein the processing includes processing the first image to determine whether the fingerprint is a legitimate fingerprint. 
     
     
       9. The method of  claim 7 , wherein the processing includes validating the fingerprint using the second image. 
     
     
       10. The method of  claim 1 , wherein the second sensing region of the sensor comprises sensor electrodes disposed at a pitch less than a sensor electrode pitch of sensor electrodes disposed in the first sensing region. 
     
     
       11. The method of  claim 1 , wherein sensor electrodes of the first sensing region are electrically connected to sensor electrodes of the second sensing region. 
     
     
       12. The method of  claim 1 , wherein the multi-resolution biometric sensor includes one of a transcapacitive sensor, an absolute capacitive sensor, an optical sensor, a thermal sensor, or an ultrasonic sensor. 
     
     
       13. A biometric input device comprising:
 a sensor region having a first sensing region and second sensing region, the first sensing region having a resolution lower than a resolution of the second sensing region, wherein the second sensing region is at least partially circumscribed by the first sensing region; and 
 a processing system configured to determine biometric information from an input object in the sensor region, wherein the processing system is configured to: 
 determine a low resolution image of a first area of the input object in the sensor region using both the first sensing region and the second sensing region simultaneously, the low resolution image of the first area of the input object including an image portion of the input object imaged by the first sensing region and an image portion of the input object imaged simultaneously by the second sensing region; and 
 determine a high resolution image of a second area of the input object in the second sensing region. 
 
     
     
       14. The biometric input device of  claim 13 , wherein the processing system is configured to determine the low resolution image of the first area of the input object in the sensor region by down sampling the image portion of the input object imaged by the second sensing region. 
     
     
       15. The biometric input device of  claim 13 , wherein the input object includes a fingerprint. 
     
     
       16. The biometric input device of  claim 15 , wherein the processing system is configured to determine if the fingerprint is a legitimate fingerprint using the high resolution image. 
     
     
       17. The biometric input device of  claim 15  wherein the processing system is configured to validate an identity of the fingerprint using at least the low resolution image. 
     
     
       18. The biometric input device of  claim 15 , wherein the biometric input device comprises one of a transcapacitive sensor, an absolute capacitive sensor, an optical sensor, a thermal sensor, or an ultrasonic sensor. 
     
     
       19. The biometric input device of  claim 13 , wherein the second sensing region comprises sensor electrodes disposed at a pitch less than a sensor electrode pitch of sensor electrodes disposed in the first sensing region. 
     
     
       20. An electronic device comprising:
 a fingerprint sensor having a first sensing region and second sensing region, the first sensing region having a resolution lower than a resolution of the second sensing region, wherein the second sensing region is at least partially circumscribed by the first sensing region; and 
 a processing system communicably coupled with the fingerprint sensor, the processing system configured to determine biometric information from a fingerprint proximal the fingerprint sensor, wherein the processing system is configured to: 
 determine a low resolution image of a first area of the fingerprint using both the first sensing region and the second sensing region simultaneously, the low resolution image of the first area of the fingerprint including an area of the fingerprint imaged by the first sensing region and an area of the fingerprint imaged simultaneously by the second sensing region; and 
 determine a high resolution image of a second area of the fingerprint in the second sensing region. 
 
     
     
       21. The electronic device of  claim 20 , wherein the second area of the fingerprint comprises at least a portion of the first area of the fingerprint. 
     
     
       22. The biometric input device of  claim 13 , wherein the second area of the input object comprises at least a portion of the first area of the input object.